This invention relates to a motor vehicle with an engine mounted on a front side thereof to drive front wheels (FF type) having a continuously variable transmission, and more particularly, to a structure of the continuously variable transmission operatively and longitudinally connected to the engine and the transmission. And further, the prevent invention relates to a power unit for a four wheel drive motor vehicle of the same FF type.
Such a motor vehicle as having the engine longitudinally mounted on the motor vehicle and of the FF type has been known in the prior art. In the case of an automatic transmission type, the transmission for automatically changing an output shaft speed of the transmission is provided in the transmission.
In FIG. 7, a transmission having a conventional automatic transmission will be described. First, an engine 5 is mounted longitudinally on a motor vehicle body in an engine compartment 2 of a motor vehicle 1, a transmission 20 is operatively connected to the engine 5, and a torque converter 33, an automatic transmission 91, etc., are operatively connected in series with the engine 5. In the case where the entire length of the engine is short like a horizontally opposed type engine, a V-type engine, the engine 5 is disposed at a relatively forward side. Thus, a predetermined distance is assured between a rear end of the engine 5 and a toe board for partitioning the engine compartment 2 and a passenger room 3. Further, a transmission 20 in which a front differential 80 is interposed between a torque converter 33 and an automatic transmission 91 in an integral structure in consideration of a motor vehicle structure, a front wheel position, and etc. has been known.
In this type of the transmission 20, a steering gear box 6 is arranged directly under the torque converter 33, and a cross member 7 as a motor vehicle structural member is arranged on a periphery of the steering gear box 6. Thus, the front differential 80 is arranged at a position not interfered with the torque converter 33, the steering gear box 6 and the cross member 7, and axles for transmitting power to the right and left sides of the front differential 80 can be operatively connected to front wheels 8 at an optimum position without interface.
However, since the automatic transmission 91 is extended in a large length rearwardly in the transmission 20, the automatic transmission 91 encroaches upon the passenger room 3 from the toe board 4. Recently, the automatic transmission 91 becomes large because the number of stages of reduction gears increases. And a tunnel 14 having a relatively large sectional area is formed in the passenger room 3, and hence the automatic transmission 91 is housed in the tunnel 14 in a state encroaching upon the passenger room 3. Therefore, a resident range of the passenger room 3 is narrowed, and arrangements of an accelerator pedal 9, a brake pedal 10, etc., are limited. In addition, the toe board 4 is the partition in which a heavy matter cannot be mounted, and a space of the toe board 4 is not effectively utilized.
For automatically changing an output shaft speed of the transmission, a continuously variable transmission has been already proposed. According to the continuously variable transmission, the output shaft speed of the transmission is continuously changed, and hence power is not shut off, thereby improving a power transmitting efficiency. Further, output characteristics of the engine can be sufficiently utilized to improve a practical fuel consumption and to smoothly change the output shaft speed of the transmission without shift shock. Since a large ratio of speed difference can be set with a basic size, there is an advantage that a high reduction gear ratio at the time of cruising and preferable starting characteristics are compatible.
Further, the continuously variable transmission fundamentally has a primary pulley, a secondary pulley and a drive belt wound on both the pulleys in a very compact structure in which its axial length is shortened. Further, the secondary pulley can be arranged at an arbitrary position on a periphery of the primary pulley to provide advantages such as an increase of design freedom, an appropriate installation of a power transmission passage after the secondary pulley, etc. Then, a number of effects are expected by employing a continuously variable transmission as a transmission of an engine longitudinally mounted via the transmission.
Heretofore, as a transmission having a continuously variable transmission longitudinally mounted via the transmission, Japanese Patent Laid-Open Publication No. 89068/1976 is, for example, disclosed. In the continuously variable transmission, an output pulley is arranged under an input pulley, an output shaft of the output pulley is extended straightly to an engine side, and operatively connected to a differential arranged directly under the engine.
In Japanese Patent Laid-Open Publication No. 96654/1979, an engine is operatively connected to a continuously variable transmission via a centrifugal clutch and a forward/reverse changeover planetary gear mechanism. Further, a belt wheel at an input side of the continuously variable transmission is operatively connected to an axle through a clutch, and a belt wheel of an output side is operatively connected to the axle through a clutch and a gear unit.
In Japanese Patent Laid-Open Publication No. 150539/1990, a secondary shaft of a continuously variable transmission is extended forwardly as a drive system of a front engine front and rear wheel drive part time vehicle, and operatively connected to a front wheel drive shaft through a pair of reduction gears. A differential case is arranged under a housing having a torque converter, a front differential is housed in the case, and a front wheel drive shaft is operatively connected to the front differential.
However, since the first prior art has a type in which the forward/rearward changeover apparatus is arranged at the output side of the continuously variable transmission, the continuously variable transmission is driven even at a neutral position to deteriorate power loss, fuel consumption, etc. Further, since the output pulley having a large shape, the forward/rearward changeover apparatus and the differential are arranged under the engine, an entire height is raised to cause various defects in an actually mounted state.
Since the second prior art is the rear wheel drive type by the engine mounted on the rearside of the vehicle, this cannot be applied to the FF type of the present invention.
Since the third prior art has a type in which the secondary shaft is operatively connected to the front differential via the pair of reduction gears, number of degrees of freedoms of determining a reduction gear ratio and a positional relationship between the secondary shaft and the front differential is defective. Since the front differential is arranged under the torque converter, an entire height is raised similarly to the first prior art in the case of mounting in the motor vehicle.
A four wheel drive motor vehicle having a power unit longitudinally mounted on the motor vehicle and a part time or a full time drive four wheel system of a front engine front wheel drive type has been known in the prior art. In this case, in an automatic transmission type, a transmission for automatically changing an output shaft speed of the transmission is provided in the transmission portion of the power unit.
In FIG. 12, a power unit of a four wheel drive motor vehicle having a conventional automatic transmission will be described. First, a power unit 100 having an engine 5 is mounted longitudinally of a motor vehicle body in an engine compartment 2 of a motor vehicle 1. A torque converter 33, an automatic transmission 101 and a transfer apparatus 90 are connected and coaxially arranged to the engine 5 in the power unit 100. In the case where the entire length of the engine is short with a horizontal opposed type engine, or a V-type engine, the engine 5 is mounted at a relatively forward side. Thus, a predetermined distance is assured between a rear end of the engine 5 and a toe board for partitioning the engine compartment 2 and a passenger room 3. Further, an automatic transmission 100A in which a front differential 80 is interposed between a torque converter 33 and an automatic transmission apparatus 101 in an integral structure in consideration with a distance between the engine 5 and the toe board 4, a motor vehicle body structure, a front wheel position, has been known.
According to the automatic transmission 100A, a steering gear box 6 is arranged directly under the torque converter 33, and a cross member 7 as a motor vehicle structural member is arranged on a periphery of the steering gear box 6. Thus, the front differential 80 is arranged at a position without interference by the torque converter 33, the steering gear box 6 and the cross member 7, and axles to be output to the right and left sides of the front differential 80 can be operatively connected to the front wheels 8 arranged at the optimum position.
However, in the automatic transmission apparatus 101 of the automatic transmission 100A, mechanical components 101a of a planetary gear, a clutch and a brake, and a valve block 101b to be controlled at a reduction gear ratio are extended rearwardly in a large length and in a large sectional area. Therefore, the automatic transmission apparatus 10 having a large volume occupies in the passenger room 3 from the toe board 4. Recently, as the automatic transmission apparatus 101 becomes large for containing number of the reduction gears, a tunnel 14 having a relatively large sectional area is formed in the passenger room 3, and hence the automatic transmission apparatus 101 is housed in the tunnel 14 in a state encroaching upon the passenger room 3. Therefore, the space of the passenger room 3 is narrowed, and arrangements of an accelerator pedal 10, a brake petal 9, and etc., are limited. In addition, the toe board 4 is the partition in which a heavy component cannot be mounted, and a space of the toe board 4 is not effectively utilized.
As a transmission for automatically changing an output shaft speed of the transmission, a continuously variable transmission has been already proposed. In the continuously variable transmission, the output shaft speed of the transmission is continuously changed, and hence the power is not shut off, thereby improving a power transmitting efficiency. Further, output characteristics of the engine can be sufficiently utilized to improve a practical fuel consumption and to hence smoothly change the output shaft speed of the transmission without shift shock. Since a large speed shift ratio can be set with a basic size, there is an advantage that a high reduction gear ratio at the time of cruising and preferable starting characteristics are compatible.
Further, the continuously variable transmission fundamentally has a primary pulley, a secondary pulley and a drive belt wound on both the pulleys in a very compact structure in which its axial length is shortened. Further, the secondary pulley can be arranged at an arbitrary position on a periphery of the primary pulley to provide advantages such as an increase of design freedom, an easy installation of a power transmission passage after the secondary pulley, etc. Then, a number of effects are expected by employing a continuously variable transmission by longitudinally mounting the transmission.
Heretofore, as a four wheel drive motor vehicle of a front engine front wheel drive type having a power unit assembled with a continuously variable transmission longitudinally mounted via the engine, Japanese Patent Laid-Open Publication No. 150539/1990 is, for example, disclosed. In this prior art, a continuously variable transmission has a primary pulley of an input side and a secondary pulley of an output side mounted in vertical direction. A secondary shaft is extended forwardly, and operatively connected to a front drive shaft through a pair of reduction gears. A front differential is housed in a differential case under a housing having a torque converter, and the front drive shaft is operatively connected to transmit power to the front differential. On the other hand, a speed reduction apparatus having a changeover brake is operatively connected to a rear portion of the secondary shaft, and power is transmitted from the speed reduction apparatus to a rear differential through a propeller shaft, etc.
However, since the prior art has a structure in which the primary pulley, the secondary pulley of the continuously variable transmission, the torque converter, and the front differential are arranged in the vertical direction, an entire height becomes high. In the case where they are mounted in the motor vehicle so as not to interfere with the steering gear box and the cross member, it is required to modify a vehicle body structure. Since the reduction gear and the speed reduction apparatus are divided and mounted at the front and the rear portions of the secondary shaft, the structure and the space are disadvantageous. Further, there is a defect that a power output position of a rear wheel side is limited by the mounted secondary pulley.